This is a bug of the UK English translation. GameForge decided to name Kishar Combatants as Kishar Fighter, so they look like you need them for this quest, but that's wrong. What you actually need to kill is the NPC with the ID 219051. This is the only Kishar Fighter that should and does count for this quest. Since the othertwo IDs don't have matching names in other client languages, we won't change the quest to let them also count.